In order to make the user easily tread the treadmill belt and push the treadmill belt rearward to achieve a labor-saving effect, the manufacturing process of the existing curved treadmill deck is complicated. It is formed by gluing multiple layers of thin boards to a certain thickness to form a flat deck, and then the flat deck is heated and pressed by a large-sized oil hydraulic press to form a curved treadmill deck with a mold. However, the process of the molding needs time, so the piece of work is rather time-consuming. Besides, the arc angle must be a certain angle for the curved treadmill deck to be mounted to a specific curved side frame. If the curved side frames at both sides of the treadmill are slightly asymmetric, the assembly is quite troublesome. Because the curved treadmill deck has been hardened and shaped, it is necessary to adjust the position of the fixing seat of the curved side frame. This is quite time-consuming.
The aforementioned hardened treadmill deck cannot achieve a buffer effect, and is likely to cause harm to the knee of the user. A buffer mechanism may be used to remedy the defect. However, the buffer mechanism will have a rebound effect when the user lifts his/her feet, which may directly hurt the ankle or knee. Because the feet bear the weight of the body, the reaction force is large. The buffer mechanism functioning as a buffer is not beneficial for the feet, and it may harm the feet. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.